Contact assembly

ABSTRACT

A contact assembly for limiting the transfer-current density in a rotary-type plating apparatus for electroplating a metal onto one side of a moving sheet is disclosed. The contact assembly has a contact member on the periphery of the rotatable member of the plating apparatus, which contact member is engageable with the unplated side of the sheet during the path of movement of the sheet through the electrolyte and makes electrical contact with the sheet. The contact member has a contact edge. Sealing means are adjacent the contact member on the rotatable member for receiving an outer edge of the sheet and for sealing the unplated side of the sheet from the electrolyte and for maintaining the cumulative plating current in the sheet and for guiding the cumulative plating current toward the contact member. The sealing member has a sealing edge in sealing engagement with the contact edge of the contact member, thereby forming a contact assembly seal. The contact member has a reduced portion adjacent the end of the contact assembly seal adjacent the contact edge. The reduced portion has a high resistance and a low conductance so that a portion of the cumulative plating current is carried by the reduced portion and the remainder of the cumulating plating current is carried by the sheet so that the transfer current density in the reduced portion is below the hot-spot-producing level in the sheet and below the pickled-band-producing level in the reduced portion. The contact member also has a substantially full portion adjacent the other end of the contact assembly seal. The full portion has a lower resistance than the resistance of the reduced portion and a higher conductance than the conductance of the reduced portion so that the transfer current adjacent the full portion is substantially the residual cumulative plating current in the sheet. The contact member also has an intermediate portion intermediate the reduced portion and the full portion for increasing the transfer current density into the contact member between the reduced portion and the full portion.

Jan. 11, 1972 D. T. CARTER 3,634,223

CONTACT ASSEMBLY Filed Feb. 25, 1970 3 Sheets-Sheet 1 FIG. f

94 Li 94o 4 Electrolyte Electrolyte Flow Flow *3 6H0 I r r &\ i I I l V -24 w H l H 98 m9 25 20 l i L=270 Return to Recirculating and I8 I07 I00 Storage Tank t Electrolyte 20 Return to Recirculating and Storage Tank I 0 36 [0c 6 30 I0 36 a Return to Recir- I09 cu/at/ng and i 28 Stem e Tank t I090 7 Cooling 6820 20 Cooling Water Out Water In Return to Rec/rcu/ating and J l/VVENTOR DAN/EL r. CARTER 7 36 26 30 I0 32 I09 36 By United States Patent O 3,634,223 CONTACT ASSEMBLY Daniel T. Carter, Penn Township, Westmoreland County, Pa., assignor to United States Steel Corporation Filed Feb. 25, 1970, Ser. No. 14,150 Int. Cl. C231) /68 U.S. Cl. 204-206 14 Claims ABSTRACT OF THE DISCLOSURE A contact assembly for limiting the transfer-current density in a rotary-type plating apparatus for electroplating a metal onto one side of a moving sheet is disclosed. The contact assembly has a contact member on the periphery of the rotatable member of the plating apparatus, which contact member is engageable with the unplated side of the sheet during the path of movement of the sheet through the electrolyte and makes electrical contact with the sheet. The contact member has a contact edge. Sealing means are adjacent the contact member on the rotatable member for receiving an outer edge of the sheet and for sealing the unplated side of the sheet from the electrolyte and for maintaining the cumulative plating current in the sheet and for guiding the cumulative plating current toward the contact member. The sealing member has a sealing edge in sealing engagement with the contact edge of the contact member, thereby forming a contact assembly seal. The contact member has a reduced portion adjacent the end of the contact assembly seal adjacent the contact edge. The reduced portion has a high resistance and a low conductance so that a portion of the cumulative plating current is carried by the reduced portion and the remainder of the cumulating plating current is carried by the sheet so that the transfer current density in the reduced portion is below the hotspot-producing level in the sheet and below the pickledband-producing level in the reduced portion. The contact member also has a substantially full portion adjacent the other end of the contact assembly seal. The full portion has a lower resistance than the resistance of the reduced portion and a higher conductance than the conductance of the reduced portion so that the transfer current adjacent the full portion is substantially the residual cumulative plating current in the sheet. The contact member also has an intermediate portion intermediate the reduced portion and the full portion for increasing the transfer current density into the contact member between the reduced portion and the full portion.

BACKGROUND OF THE INVENTION Heretofore, conductor rolls employed in a radial-type plating cell have been of the type shown in FIGS. 20-22 of U.S. Pat. 3,483,113, issued Dec. 9, 1969, to applicant and assigned to United States Steel Corporation. Such a conductor roll consists of a low carbon steel body having a stainless steel contact ring secured to the roll body and resilient sealing bands formed of rubber or the like covering the roll body and lapped over the contact ring, as shown particularly in FIG. 22 of the above mentioned patent, to effect a seal between the sealing band and the contact ring.

With a conventional conductor roll, a high transfer current density occurs approximately /2 to 1" from the edge of the contact ring. If the transfer current density were uniform over the entire contact ring surface, the transfer current density would be about 8.05 amperes per square inch for a plating cell having about a 5 foot diameter, and about 25,000-ampere capacity. The actual transfer-current density at a distance at about /2 to 1" from the edge of the contact ring is approximately 48 ice amperes per square inch. This high current density is due to the sheet plating current load outside the contact ring and the difference in total conductivity between the strip being plated and the contact ring on the conductor roll. The contact ring on the conductor roll in conventional insulations is a better total conductor than the strip. As a result, the majority of the plating current travels to the edge of the contact ring, then transfers to the strip, thereby resulting in a high transfer current density at the edge of the contact ring. This high transfer current density causes hot spots in the strip and an uncleaned pickled band on the edge of the contact ring.

Further, the adhesive bond between the rubber resilient sealing band and the stainless steel contact ring often fails thereby permitting the high acid electrolyte (about 8% acid) to seep under the rubber sealing band and to attack the low carbon steel in the conductor roll body. The resultant loss of bond between the sealing bands and the contact ring will permit foreign materials to gather under the sealing ring, thereby elevating the sealing ring in a circumferential band near the edge of the stainless steel contact ring with attendant distorted strip shapes.

I am aware of conventional plating apparatus and methods shown in the following patents:

OBJECTS OF THE INVENTION It is the general object of this invention to avoid and overcome the foregoing and other difliculties of and objections to prior art practices by the provision of an improved sealing band-contact ring assembly for a conductor roll for a radial type plating cell, which assembly:

(a) Improves the uniformity of the transfer current density between the contact ring and the strip;

(b) Has an improved seal between the edge of the contact ring and the edge of the associated sealing band;

(c) Eliminates hot spots in the strip;

(d) Has a longer conducting surface life due to the elimination of damage to the conducting surface caused by spot high contact current densities;

(e) Substantially eliminates the unclean pickled band on the edge of the contact ring adjacent the sealing band;

(f) Prevents seepage of the electrolyte through the seal between the contact ring and the sealing band thereby preventing acid attack of the low carbon steel in the conductor roll body; and

(g) Prevents the entrance of foreign materials between the sealing band and the contact ring thereby preventing the raising of the sealing rings adjacent the edges of the contact ring and preventing distorted shapes in the strip being processed.

BRIEF SUMMARY OF THE INVENTION The aforesaid objects of this invention and other objects which will become apparent as the description proceeds are achieved by providing an improved contact assembly for a rotary-type plating apparatus. This contact assembly has a contact member on the periphery of the rotatable member of the plating apparatus, which contact member is engageable with the unplated side of the sheet (or the plated side of the sheet when making a twoside coating) during the path of movement of the sheet through the electrolyte and makes electrical contact with the sheet. The contact member has a contact edge. Sealing means are adjacent the contact member on the rotatable member for receiving an outer edge of the sheet and for sealing the unplated side of the sheet from the electrolyte and for maintaining the cumulative plating current in the sheet and for guiding the cumulative plating current toward the contact member. The sealing member has a sealing edge in sealing engagement with the contact edge of the contact member, thereby forming a contact assembly seal. The contact member has a reduced portion adjacent the end of the contact assembly seal adjacent the contact edge. The reduced portion has a high resistance and a low conductance so that a portion of the cumulative plating current is carried by the reduced portion and the remainder of the cumulating plating current is carried by the sheet so that the transfer current density in the reduced portion is below the hot-spot-producing level in the sheet and below the pickled band producing level in the reduced portion. The contact member also has a substantially full portion adjacent the other end of the contact assembly seal. The full portion has a lower resistance than the resistance of the reduced portion and a higher conductance than the conductance of the reduced portion so that the transfer current adjacent the full portion is substantially the residual cumulative plating current in the sheet. The contact member also has an intermediate portion intermediate the reduced portion and the full portion for increasing the transfer current density into the contact member between the reduced portion and the full portion.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS For a better understanding of this invention, reference should be had to the accompanying drawings, wherein like numerals of reference indicate similar parts throughout the several views and wherein:

FIG. 1 is a side elevational view, partially diagrammatic, showing a rotary plating apparatus for electroplating a metal onto one side of a moving sheet, which apparatus contains the improved contact assembly of this invention;

FIG. 2 is a horizontal sectional view taken along the lines 22 of FIG. 1 in the direction of the arrows;

FIG. 3 is a fragmentary diagrammatic enlarged vertical sectional view of the improved contact assembly and showing diagrammatically the cumulative plating current, the plating currents in the sheet, and the plating currents in the contact member along the contact assembly seal of the contact assembly;

FIG. 4A is an enlarged diagrammatic fragmentary vertical sectional view of an alternative embodiment of the contact assembly and showing a serrated contact assembly seal;

FIG. 4B is a figure similar to FIG. 4A and showing a corrugated type contact assembly seal;

FIG. 4C is a view similar to FIGS. 4A, 4B and showing a concave arcuate contact assembly seal;

FIG. 4D is a view similar to FIGS. 4A-4C of another alternative embodiment of the contact assembly and showing arresting surface portions on the reduced portion and intermediate portion of the contact assembly;

FIG. 4B, similar to FIGS. 4A-4D shows a convex arcuate contact assembly seal;

FIG. 5 is a fragmentary plan view of a portion of one member of the contact member or the sealing member, in this case the contact member, provided with a plurality of various kinds of dimples or holes; and

FIG. 6 is a fragmentary diagrammatic enlarged side elevational view showing the contact member and the sealing means provided with protuberances of various kinds.

Although the principles of this invention are broadly applicable to plating apparatus, this invention is particularly adapted for use in conjunction with a rotary-type plating apparatus for electroplating a metal onto one side of a 4 moving sheet and hence it has been so illustrated and will be so described.

DETAILED DESCRIPTION With specific reference to the form of this invention illustrated in the drawings and referring particularly to FIGS. 1 and 2, a rotary-type plating apparatus for electroplating a metal, such as zinc or the like, onto one side 10a of a moving sheet 10, such as cold-rolled carbon steel sheet or the like, is indicated generally by the reference numeral 12. This apparatus 12 is of the type shown in the above mentioned US. Pat. No. 3,483,113. The reference numerals shown in FIGS. 1, 2 (but not mentioned in this description) are the same as those in such patent.

Apparatus 12 The moving sheet 10 is provided with a sheet edge such as 101;, (FIG. 2) and is mounted under tension by means of an entry roll 14 and an exit roll 16 (FIG. 1).

The apparatus 12 has tank means, such as an electrically insulated tank 18 (FIGS. 1, 2) which tank 18 is adapted to contain an electrolyte 20 (FIGS. 1-3) of the type disclosed in such US. Pat. No. 3,483,113. A rotatable member, such as the drum 22 (FIGS. 1, 2, 3) is mounted on a shaft 24 (FIGS. 1, 2) and is rotatable on bearings 27 (FIG. 2) in the electrolyte 20. Such drum 22 receives the other side 10d (FIG. 1) of the sheet 10 and guides the sheet 10 along its path of movement, as shown in FIG. 1 through the electrolyte 20. Anode means (FIGS. 1, 2, .3), such as the anode 26 (suitably formed, for example, of about 99.5% lead and the balance silver), is disposed in the electrolyte 20 adjacent the drum 22 and the unplated side 10d of the sheet 10. The anode 26 defines with the sheet 10 a cavity 29 (FIGS. 1, 2, 3). The apparatus 12 is provided with a contact assembly 28 (FIGS. 2, 3) of this invention for limiting transfer current density in the rotary type plating apparatus 12.

Contact assembly 28 The contact assembly 28 (FIG. 3) has a contact member 30 (FIGS. 2, 3) suitably a contact ring formed of stainless steel, nickel, or the like, mounted on a carbonsteel body 32 (FIGS. 2, 3) of the drum 22. Carpenter 20Cb3 alloy stainless steel manufactured by Carpenter Steel Company, Reading, Pa., is a suitable material for the contact ring 30. The contact member or ring 30 is engageable with the unplated side 10d of the sheet 10 during the path of movement of the sheet 10 through the electrolyte 20 and makes electrical contact with the sheet 10. The contact member 30 has a contact edge 34 (FIG. 3). Sealing means, such as the resilient sealing bands 36 (FIGS. 2, 3 formed of rubber, neoprene or the like), are disposed adjacent the contact member 30 on the low carbon steel body 32 (such as type 1020 steel or the like) of the drum 22 for receiving the sheet edges 10b (FIG. 3) and 100 (FIG. 2) and for sealing the unplated side 10d of the sheet 10 from the electrolyte 20, for maintaining the cumulative plating current in the sheet 10 and for guiding the cumulative plating current I (FIG. 3) toward the contact member 30, as shown in FIG. 3. Neoprene synthetic rubber manufactured by E. I. du Pont de Nemours, Wilmington, Del., is a suitable material for the sealing bands 36. The sealing member or band 36 has a sealing edge 38 (FIG. 3) which is disposed in sealing engagement by means of an adhesive 40 (for example, Typly ambient temperature adhesive manufactured by Marbon Chemical, Division of Borg-Warner Corporation, Gary, Ind., with the contact edge 34 to form a contact assembly seal 42 (FIG. 3).

As shown in FIG. 3, the contact member 30 has a reduced portion 44 adjacent the right-hand end, as viewed in FIG. 3, of the contact assembly seal 42 adjacent the contact edge 34 of contact member 30. The reduced portion 44 has a high resistance and low conductance so that a portion I of the cumulative plating current I is carried by the reduced portion 44 and the remainder 1, of the cumulative plating current I is carried by the sheet 10 so that the transfer current I in the reduced portion 44 is below the hot-spot-producing level in the sheet 10 and below the pickled-band-producing portion in the reduced portion 44.

The contact member 30 also has a substantially full portion 46 (FIG. 3) adjacent the left-hand end, as viewed in FIG. 3, of the contact assembly seal 42. This full portion 46 has a lower resistance than the resistance of the reduced portion 44 and a higher conductance than the conductance of the reduced portion 44 so that the transfer current 1, adjacent the full portion 46 is substantially the current 1,, in the sheet 10.

The contact member 30 has an intermediate portion 48 (FIG. 3) intermediate the reduced portion 44 and the full portion 46 for increasing the current 1 1 etc. in the contact member 30 between the reduced portion 44 and the full portion 46.

FIG. 3 shows a typical set of values for the cumulative plating current 1 the transfer currents I Itz, etc. the current in the sheet 1 I etc., and the current I 1 etc. in the contact member 30 along the contact assembly seal 42.

Suitable dimensions (FIG. 3) for a typical contact assembly seal 42 are shown in the following table:

Alternative embodiments It will be understood by those skilled in the art that alternatively the following adhesives may be employed:

Trade name or trademark Manufacturer USS Nexus S8005"thermosetting USS Chemicals, Division United epoxy based two-component ad- States Steel Corporation, Pittshesivc (ambient cured) burgh, Pa. Isocinate adhesive and eurethane Dayton Chemical Laboratories,

adhesive. West Alexandria, Ohio. Do Hughson Chemical Company, i31- vision of Lord Manufacturing C(bmpany, Erie, Pa.

Chemlox adhesive In FIG. 4A, the contact member or ring 30 and the sealing band 38 are provided respectively with a serrated contact edge 34 and sealing edge 38%, to form a generally serrated contact assembly seal 42.

FIG. 4B shows a generally corrugated type contact assembly seal 42 In FIG. 4C a generally concave arcuate contact assembly seal 42 is shown. This contact assembly seal 42 may be circular, elliptical, hyperbolical, parabolical, or the like.

For the purpose of slowing up the conductance of the transfer current I in the contact member 30 (FIG. 4D) along the contact assembly seal 42, arresting surfaces or protuberances 50 may be provided on the resilient sealing bands 36 or contact assembly seal 42. Similarly, if for any reason it is desirable to increase the conductance of the transfer current I into the contact member 30, promoting surfaces or dimples 52 (FIG. 4D) or the like may be provided on the reduced portions 44 and intermediate portions 48 or in the contact assembly seal 42 FIG. 4B shows a convex arcuate contact assembly seal 42 It will be understood for a consideration of FIG. 5 that either the contact member 30 as shown in FIG. 5, or the sealing bands 36 (not shown in FIG. 5) may be provided with a plurality of dimples to increase the adhesive bond between the contact member 30 (FIG. 5) and the sealing band 36, not shown in FIG. 5. The dimples 54 may be (as shown in FIG. 5) circular holes 54a, slots 54b, square or rhombic holes 540, cross holes 54d, mesh holes 542, zig-zag holes 54;, corrugated holes 54g or the like.

Also, for the purpose of improving the adhesive bond between the contact member 30 and the sealing band 36 one of the contact member 30 and the sealing band 36 (in this case, the contact member 30 may be provided with protuberances. In FIG. 6 are shown protuberances, such as the divergent prong type protuberances 56a, frusto-spherical hollow protuberances 56b, frustoconical hollow protuberances 56c, hollow cylindrical protuberances 56d, parallelepiped type protuberances 56e, pointed protuberances 56 round protuberances 56g, or the like.

Summary of the achievements of the objects of the invention It will be recognized by those skilled in the art that the objects of this invention have been achieved by providing an improved contact assembly 28 (FIGS. 1-3), 28 (FIG. 4A), 28 (FIG. 4B), 28" (FIG. 4C), 28 (FIG. 4D), 28 (-F-IG. 4E), which improved contact assemblies improve the uniformity of the transfer current In, I etc. (FIG. 3) between the contact ring or member 30 and the strip or sheet 10; provide an improved contact assembly seal 42 between the contact edge 34 of the contact ring 30 and the sealing edge 38 of the sealing band 36; eliminate hot spots in the strip or sheet 10 adjacent the sealing band 36; have a longer conducting surface life due to the improved transfer efiiciency; substan tially eliminate the unclean pickled band on the edge of the contact ring 30 adjacent the sealing band 36; pre vent seepage of electrolyte 20 through the contact assembly seal 42 thereby preventing acid attack on the low carbon steel body 32 of the drum 22; and prevent the entrance of foreign materials, such as dirt or the like, between the sealing bands 36 and the contact ring 30 thereby preventing the raising of the edges of the sealing rings 36 adjacent the edges of contact ring 30 and preventing distorted shapes in the strip or sheet 10 being processed by the apparatus 12.

While in accordance with the patent statutes, preferred and alternative embodiments of this invention have been illustrated and described in detail, it is to be particularly understood that this invention is not limited thereto or thereby.

I claim:

1. A rotary type plating apparatus for electroplating a metal onto one side of a moving sheet provided with a sheet edge and being under tension, said apparatus having:

(A) tank means adapted to ocntain an electrolyte;

(B) a rotatable member rotatable in said electrolyte and for receiving the other side of said sheet and for guiding said sheet along a path of movement through said electrolyte;

(C) anode means in said electrolyte adjacent said rotatable member and the other side of said sheet; and

(D) a contact assembly on said rotatable member; said contact assembly having:

(a) a contact member on the periphery of said rotatable member and engageable with said other side of said sheet during said path of movement through said electrolyte to make electrical contact with said sheet,

said contact member having a contact edge,

and

(b) a sealing member adjacent said contact member on said rotatable member for receiving said sheet edge and for sealing said other side of said sheet from said electrolyte and for maintaining the cumulative plating current in said sheet and for guiding said sheet toward said contact member,

(1) said sealing member having a sealing edge in sealing engagement with said contact edge to form a contact assembly seal,

(2) said contact member having a reduced portion adjacent the end of said contact assembly seal adjacent said sheet edge, said reduced portion having a high resistance and low conductance so that a portion of said cumulative plating current is carried by said reduced portion and the remainder of said cumulative plating current is carried by said sheet so that the transfer current density in said reduced portion is below the hot-spot-producing level in said sheet and below the pickled-band-producing level in said reduced portion,

(3) said contact member also having a substantially full portion adjacent the other end of said contact assembly seal, said full portion having a lower resistance than the resistance of said reduced portion and a higher conductance than the conductance of said reduced portion so that the transfer current density adjacent said full portion is substantially the residual cumulative plating current in said sheet,

(4) said contact member having an intermediate portion intermediate said reduced portion and said full portion, said intermediate portion having a gradient resistance between the resistance of said reduced portion and said full portion and a gradient conductance between the conductance of said reduced portion and said full portion to gradually increase the transfer current density into said contact member between said reduced portion and said full portion.

2. A contact assembly for limiting transfer-current density in a rotary-type plating apparatus for electroplating a metal onto one side of a moving sheet provided with a sheet edge and being under tension and having tank means adapted to contain an electrolyte, a rotatable member rotatable in said electrolyte and for receiving the other side of said sheet and for guiding said sheet along a path of movement through said electrolyte, and anode means in said electrolyte adjacent said rotatable member and said one side of said sheet, said contact assembly having:

(a) a contact member on the periphery of said rotatable member and engageable with said other side of said sheet during said path of movement through said electrolyte to make electrical contact with said sheet,

said contact member having a contact edge, and

(b) a sealing member adjacent said contact member on said rotatable member for receiving said sheet edge and for sealing said other side of said sheet from said electrolyte and for maintaining the cumulative plating current in said sheet and for guiding said cumulative plating current toward said contact member,

(1) said sealing member having a sealing edge in sealing engagement with said contact edge to form a contact assembly seal,

(2) said contact member having a reduced portion adjacent the end of said contact assembly seal adjacent said sheet edge,

said reduced portion having a high resistance and low conductance so that a portion of said cumulative plating current is carried by said sheet so that the transfer current density in said reduced portion is below the hot-spot-producing level in said sheet and below the pickel-band-producing level in said reduced portion,

(3) said contact member also having a substantially full portion adjacent the other end of said contact assembly seal,

said full portion having a lower resistance than the resistance of said reduced portion and a higher conductance than the conductance of said reduced portion so that the transfer current density adjacent said full portion is substantially the residual cumulative plating current in said sheet,

(4) said contact member having an intermediate portion intermediate said reduced portion and said full portion, said intermediate portion having a gradient resistance between the resistance of said reduced portion and said full portion and a gradient conductance between the conductance of said reduced portion and said full portion to gradually increase the transfer current density into said contact member between said reduced portion and said full portion.

3. The contact assembly recited in claim 2 wherein said contact assembly seal is corrugated.

4. The contact assembly recited in claim 2 wherein said contact assembly seal is concave arcuate.

5. The contact assembly recited in claim 2 wherein said contact assembly seal has an arresting portion.

6. The contact assembly recited in claim 2 wherein one edge of said sealing edge and said contact edge is provided with a plurality of dimples.

7. The contact assembly recited in claim 2 wherein one edge of said sealing edge and said contact edge has a plurality of protuberances.

8. The contact assembly recited in claim 2 wherein said contact assembly seal has a promoting portion.

9. The contact assembly recited in claim 2 wherein said contact assembly seal is convex arcuate.

10. The contact assembly recited in claim 2 wherein said contact assembly seal is serrated.

11. The contact assembly recited in claim 2 and having an adhesive between said contact edge and said sealing edge.

12. The contact assembly recited in claim 11 wherein said adhesive is an ambient temperature setting adhesive.

13. The contact assembly recited in claim 11 wherein said adhesive is a thermal setting adhesive.

14. The contact assembly recited in claim 11 wherein said adhesive is an adhesive film.

References Cited UNITED STATES PATENTS 2,927,889 3/1960 Clinehens 204211 JOHN H. MACK, Primary Examiner W. I. SOLOMON, Assistant Examiner 

